Air-type circuit interrupter



Aug 24,v 1954 R c. DlcKlNsoN nu. 2,587,451

AIR-TYPE: CIRCUIT INTERRUPTER I Filed Feb. 23, 1949 2 SheeIs-Sheet l 22 24 "'III v Patented Aug. 24, 1954 UNITED STATES PATENT OFFICE 2,687,461 AIR-TYPE CIRCUIT INTERRUPTER Robert C. Dickinson and Russell E. Frink, Pittsburgh, Pa., Corporation, Eas tion of Pennsylvania Application February 23, 1949, Serial No.

(Cl. 20G-144) circuit interrupters plates of insulating material.

ment of the arc is obtained by a produced by a magnetic blowout coil and magnetic eld poles. This magnetic eld is also re- Lateral move- A more specific object is to provide an improved spacing arrangement of the spaced plates of a circuit interrupter of magnetic field Another object is to provide an improved plate conguration to restrict the exhaust passages between the plates at the exhaust end of the arc chute.

Further objects and advantages will readily` asslgnors to Westinghouse Electric t Pittsburgh, Pa., a corpora- Fig. 3 is an enlarged plan view of one of the arc-extinguishing plates forming the arc-extinguishing structure; and

Fig. 4 shows a side elevational View of a modified type plate of wedge-shaped configuration.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral I generally designates suitable contact structure which, when separated to the open circuit position, establishes an arc which is moved upwardly into an arc chute, generally designated by the as a result of the transverse magnetic iield set up by the blowout coil 3 and associated magnet structure 4. A rotatable Contact arm 5 carries a. conducting bridge il which, in position, as shown in Fig. l,

A contact stud stationary main contact 1, through an insulating bushing I0 to the external circuit. rljhe contact stud for the stationary main contact 8 is not shown, but it may be identical to the contact stud 9.

Consequently, in the closed circuit position of the interrupter, as shown in Fig. 1, the electrical circuit comprises the contact stud 9, stationary 1, conducting bridge 6, stationary 8, to the Contact stud therefor, not external circuit.

main contact shown, to the During the of conducting bridge 6 from the main contacts t.

When the arcing contacts I I, i2 separate, the arc formed therebetween will expand upwardly member I 8, and the other arc terminal will be transferred to the other arc terminal member i9.

When this occurs, the blowout coil 3 will be put into series circuit and the transverse mageld set up thereby between the iield pole members I4 (Fig. 2) will move the established terminal members I 8, I 9 into the arc chute 2. The electrical circuit now comprises contact stud 9,. conductor 2d, blowout coil 3, Contact clip I5, arc terminal member I8, the arc itself, arc terminal member i exible shunt 28, contact arm -i to the other contact stud, not shown.

The arc chute 2 comprises an insulating rectangularly shaped housing member strips 2li space a plate 2E, composed of an insulating material, away from the plate 24. The plate 2t may have a plurality of apertures 2l formed therein which facilitate the venting of arc gases therethrough, particularly when high currents are to be interrupted. Two more insulating spacer strips 25 space the plate 2e from a plurality of plates 29, forming a unitary plate assembly. The plates 29 are composed preferably of a refractory insulating material, such as a Zircon porcelain, which does not give on gas when contacting an arc. The plates 29 have a construe tion more clearly shown in Fig. 3 and are separated by pairs of asbestos rope 35.

Above the arc terminal member i9 is a second insulating plate 2li, which is spaced by spacer strips 25 from the right-hand plate 29 of the plate assembly. Two additional spacer strips space the right-hand plate 26 from a refractory plate, not shown, which is, in turn, separated from the right-hand end of the housing 22 by a plurality of strips of fish paper.V Bolts 33a socure the several strips 25, plate 25 and the hous-` ing 22 to the plate 2i. Bolts 34a secure the righthand plate 25 and its spacer strips 25 and fish paper strips to the housing 22.

The plates 22 and the spacer strips 35 are cemented together in a preliminary process to form a unitary plate assembly which may be bodily placed into the rectangular housing 22. insulating holding strips 39 are secured by bolts (it to the opposed inner sides of the housing 22 to prevent the unitary assembly of plates 29 from being forced upwardly out of the housing 22 by the pressure of gas formed during the interrupting operation.

1laeferring to Fig. 3, which more clearly shows ze configuration of each insulating plate 29, it will be observed that each plate 29 has an inwardly extending slot or notch lli which con stricts in lateral dimension in a direction toward the top of the plate 29. Referring to Fig. 2 it will be observed that the assembling of the plates 29 is such that the upper closed ends of the slots lil are alternately staggered throughout the arc chute 2 so that when the arc is forced upwardly into the several slots il it will assume a Zig-zag configuration at the upper closed ends il of the slots lill prior to its being extinguished,

The opening operation of the interrupter will now be explained. Upon the clockwise rotation of the contact arm 5, an arc is drawn between the arcing contacts Il, l2 which quickly transfers, because of the loop circuit, to the arc tern minal members i8, i9 to thereby connect into series circuit the blowout coil 3. The magnetic field set up by the blowout coil 3 between the field pole members la sets up a transverse magnetic field through the arc chute 2, to thereby force the established arc upwardly along the are terminal members I8, i9 until it comes into contact with the closed ends il of the slots or notches it provided in the several plates 29. The magnetic field gives an upward component of velocity to the electrons which bombard gas particles and to them an upward velocity. This magnetically produced gas blast carries ionized gases upwardly to the closed ends di of the slots lil where extinction is caused by the magnetically produced upward gas blast, the exhaust gases passing upwardly between the plates 29 and out of the arc chute 2.

in prior constructions of air break circuit interrupters of this type, such as set forth in the aforesaid patent, it has been the practice to position the spacers 35 or sections of asbestos rope parallel to each other at the opposed outerside edges of each plate 29. The spacers 35 constitute a side wall means between adjacent plates 29. We have discovered, however, that considerable interrupting improvement is obtained by placing the spacers or sections of asbestos rope 33 so that a tapered constricted exhaust gas passage 62 is provided between each set of adjacent plates 22, as shown more clearly in Fig. 2. In other words, the lateral space separating the spacers 35 at the upper end of the plate 29 is smaller than the lateral space separating the spacers 35 at the lower end of the plate 29, as shown more clearly in Fig. 2.

Thus by drawing the spacers 35 in at the exhaust end of the interrupting assembly so as to gradually restrict or choke each exhaust passage d2, a considerable increase in interrupting ability has been achieved. The actual reason for this is not known with certainty at present, but the following theory may apply. It is to be clearly understood, however, that we are not limited cr bound by our present theory of the operation, because regardless of any theory proposed, there is a distinct improvement in interrupting ability achieved. We feel, however, that a possible explanation may reside in the fact that when the arc is at the upper closed ends 4l of the slots dii, it is at a very high temperature, and as the gases are travelling upwardly through the are, they pass upwardly to the exhaust end cf the arc chute, in which passage they are cooled by the surfaces of the plates 22 and contract in volume.

The reduction of the crossfsection of the gas path as the gases become progressively cooler maintains the now at high velocity and increases the turbulence and consequently the back pressure maintaining a higher pressure in the interrupting space, and also giving a more uniform motion of the arc in the slot. Even though this proposed theory may be incorrect, nevertheless the fact remains that a substantial improvement is maintained by the construction set forth in our invention without increase in size, and only a slight increase in assembly labor.

fior a particular voltage and current rating the lateral space A between the upper ends of the sections of asbestos rope 35 was 2% inches, whereas the lateral space B between the lower ends of the same pair of spacers or sections of asbestos rope 35 was 27/8 inches. The width of the plate was 3% inches.'

lig. e shows in side elevation a modified type plate This plate is wedge-shaped, as shown, and when employed in a stack with parallel spacers Se will also constrict the exhaust passage l2 between each pair of adjacent plates. rEhus the constricted exhaust passage l2 may be formed either by wedge-shaped plates alone, or by fiat parallel plates 2e with tapered spacers 35 as shown in Fig. 2, or by a combination of the two.

The foregoing description of our invention indicates how we have increased the voltage interrupting ability of plate type circuit interrupters or the type set forth in the aforesaid patent by drawing the spacers 35 together at the upper exhaust ends of the plates 29 so as to make the exhaust passages i2 more constricted at the eX- haust end or" the arc chute 2, or employing wedge? shaped plates ifi as shown in Fig. 4. We have set forth what we believe to be the best theoretical explanation for the phenomena involved but do not limit ourselves as to the correctness of said.

Although we have shown and described specic structures, it is to be clearly understood scope of the appended We claim as our invention:

1. A circuit interrupter of the air break type including an arc chute comprising a plurality of spaced plates of insulating material, each plate having a closed-end slot extending inwardly from one end thereof,

haust end of the 2. A circuit interrupter of the air-break type including an are chute comprising a plurality of plate portions, spacing means extending along each side edge of the plate portions separating adjacent plate portions a relatively short distance apart, means for establishing an arc and moving it substantially transversely against the insulating plate portions to eiect the extinction thereof, and the lateral distance between the spacing means along one side edge of the plate portions and the spacing means along the opposite side edge'of the plate portions progressively diminishing toward the exhaust end of the arc chute.

3. A circuit interrupter of the air-break type including an arc chute comprising a plurality of spaced slotted insulating plate portions separating adjacent plate portions a relatively short distance apart, means for establishing an arc and moving it substantially transversely against the plate portions and into .the slots thereof to effect the extinction thereof,

the spacing means along the opposite side edge of the slotted plate portions progressively diminishing towards the exhaust end of the arc chute.

4. A circuit interrupter of the air-break type including an arc chute comprising a plurality of short distance apart, means for establishing an arc and moving' it substantially transversely against the insulating plate portions to eiect the extinction thereof,

apart, means for establishing an arc and moving it substantially transversely against the insulating plate portions and into the slots thereof to eiect the extinction of the arc, and the lateral distance between the side wall means along one gressively diminishing toward the exhaust end of the arc chute.

6. A circuit interrupter of the air-break type including an arc chute comprising a stack of plate portions of the stack are parallel to each other thereby obtaining adequate ash-over disfor establishing an arc, means for moving the established arc substantially transversely against the plate portions to effect the extinction thereof, and the cross-sectional area of the exhaust passages through the plate portions defined by the spacing means and by the plate portions becoming progressively smaller toward the exhaust end of the arc chute.

7. vA circuit interrupter of the air-break type including anarc chute comprising a stack of spaced insulating plate portions having closed end slots therein, spacing means positioning the plate portions a relatively short distance apart to define separate exhaust passages therebetween, the median plane of each plate portion so that the end plate portions of the stack are parallel to each other thereby obtaining adequate flash-over distance at the the arc chute, means for establishing an arc, means for moving the established arc into the slots of the plate portions substantially transversely against the plate portions to effect the extinction thereof, and the cross-sectional area of the exhaust passages through the plate portions deiined by the spacing means and by the plate portions becoming progressively smaller toward the exhaust end of the arc chute.

8. A circuit interrupter of the air-break type tively short distance apart, means for establishing an arc and moving it substantially transversely against the plates to eiect the extinction thereof, and the lateral distance between each pair of spacer strips diminishing toward the exhaust end of the arc chute.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 2,215,797 Sauer Sept. 24, 1940 2,223,975 Traver Dec. 3, 1940 2,243,038 Ludwig May 20, 1941 2,243,039 Ludwig et al. May 20, 1941 2,285,643 Beiersdorf et al June 9, 1942 2,353,729 Jensen July 18, 1944 2,442,199 Dickinson et al. May 25, 1948 FOREIGN PATENTS Number Country Date 383,127 Great Britain Nov. 10, 1932 728,612 Germany Nov. 30, 1942 

